The washing of soiled fabrics with a laundry detergent composition is essentially a two step process. In the first stage the detergent must remove the soil particles from the fabric and suspend them in the soil solution. In the second stage the detergent composition must prevent the soil particles and other insolubles from redepositing on the cloth before and after the fabric is removed from the soil solution or the rinse solution. Polymers are known to aid both processes, soil release polymers enhance soil removal from the fabric whilst anti-redeposition polymers prevent the deterged soil from depositing on the fabric.
Laundry detergent compositions traditionally contain among other chemicals sodium carboxy methyl cellulose (SCMC) as an antiredeposition agent. U.S. Pat. No. 4,235,735 (Macro et al Miliken) discloses cellulose acetates with a defined degree of substitution as antiredeposition agents in laundry detergent compositions.
Other cellulosic materials have also been used in laundry detergent compositions for a variety of benefits, for example soil release and fabric care benefits.
WO 00/18861A (Unilever) and WO 00/18862A (Unilever) disclose cellulosic compounds having a benefit agent attached so that the benefit agent will be deposited on the fibres of the washed textiles during the laundry process.
In order to establish effective antiredeposition properties a high degree of substitution is required in order to make these molecules soluble, for example SCMC with a degree of substitution of 0.2 does not dissolve in water. It is known in the art that SCMC with a degree of substitution of about 0.5 and above dissolves, and it functions as an antiredeposition agent. However, because of the higher degree of substitution it is not readily biodegradable.
It has now been found that use of anionic alkyl derivatives of polysaccharides with a low degree of substitution, namely of from 0.005 to 1, provides for a readily biodegradable polymer. In addition, as such polymers are also soluble, they have been found to provide for the promotion of antiredeposition during the laundering of a textile fabric. Yet the low degree of substitution means that this antiredeposition is achieved with the added advantage of the compound itself being more biodegradable than functional equivalents.